POM-based compounds modified by mono- and bis-triazole derivatives: photocatalytic, electrochemical, and supercapacitor properties

Abstract

Five polyoxometalate-based compounds were synthesized under hydrothermal conditions, namely, {M₂(DEP)₂(H₂O)₆[H₂(TeMo₆O₂₄)]} (M = Ni 1, Zn 2), {Co(DEP)₂(H₂O)₂[H₂(γ-Mo₈O₂₆)]}·11H₂O (3), {Cu(DEP)[(H₂β-Mo₈O₂₆)_0.5]} (4), [Cu₆(DTP)₅(OH)₂(H₂O)₆(PW^VI₁₀W^V₂O₄₀)₂] (5) (DEP = 3-[1,3,4]triazol-4-ylmethyl-benzylamine, DTP = 1,4-bis(1,3,4-triazol-1-ylmethyl)-benzene). Isostructural compounds 1 and 2 are both based on Anderson anions, containing one-dimensional chain with adjacent anions linked by two [M(DEP)]²⁺ subunits. Compound 3 is based on the γ-Mo₈ anion, in which adjacent one-dimensional chains are connected by hydrogen bonding interactions to form a supramolecular two-dimensional structure. In compound 4, the β-Mo₈ anions are connected by [Cu₂(DEP)₂]²⁺ dimers to construct a chain. Two amino groups of two DEP ligands show abundant hydrogen bonding interactions with an Mo₈ anion to form two supramolecular “caps”. Compound 5 contains two kinds of Keggin anions. The coordinated anions are linked by tri-nuclear Cu clusters to form a two-dimensional layer. The dissociative PW₁₂ anions are located between adjacent layers. The 1-, 3-, and 5-CPEs show good multifunctional electrocatalytic activities. Also, compounds 2, 3, and 4 modified glassy carbon electrodes (2-, 3-, and 4-GCE) have excellent properties of supercapacitor materials. In addition, compounds 1 to 5 have good photocatalytic activities, which can not only photocatalyze the degradation of organic dyes but also photocatalyze the reduction of Cr(VI).